Electric plug



May 28, 1957 J. c. G. GRANT 2,794,094

ELECTRIC PLUG Filed May 28, 1954 2 Sheets-Sheet l 2' Q 25 ////////,E|f///////.

INVENTOR (105E CONSTANT/N0 GROJIO GRANT ATTORNEY y 1957 J. c. G. GRANT 2,794,094

ELECTRIC PLUG Filed May 28, 1954 2 Sheets-Sheet 2 INVENTOR JUJ'E CONSTANT/N0 6/?0550 GRANT ATTORNEY United States Patent ELECTRIC PLUG Jos Constantino Grosso Grant, Bnenos Aires, Argentina Application May 28, 1954, Serial No. 433,187

8 Claims. (CL 200-4155) The electric plugs known at present are essentially constituted by a box, preferably made of dielectric material, in .the accessible interior of which are provided cable connectors for fixing the ends of the cores of the electric cord, the said cable connectors communicating directly with the pins of the plug by means of electric conducting bridges having a relatively large transversal section so as to enable the electric current to flow between the inlet and outlet of the plug without the interposition of security means. When anything goes wrong in the electrical supply system as, for instance, in the case of a short circuit, and the fuses of the said system are blown out interrupting the supply of electricity, it is, as a rule, impossible to avoid the damage caused by the said short circuit to the electric gadgets in use at the moment. This fact constitutes a serious danger, especially in those cases in which the electric gadgets are constituted by delicate and expensive apparatuses as, for instance, a wireless set, a television set, a refrigerator, a washer, instruments in general etc., the lack of security means in the said devices causing inconveniences and reparation expenses. In the case of liquefiers, refrigerators, washers and other electrical gadgets for kitchen and home use as, for instance, vacuum cleaners, floor waxers, etc., in which the framework of the appliance is constituted by a conducting material, the lack of the said security means in the said bodies may be fatal for the users should anything go wrong within the appliances or cords for reasons which are well known to experts in this branch.

In order to remove these and other drawbacks as well as in order to offer the users in general greater security and, consequently, greater comfort, an electric plug has been suggested some time ago of the kind constituted by a box with at least one cable connector and at least one pin or contact element housing the said pins, characterized in that the cable connector and the pin or contact element are constituted by separate units placed at a distance from each other, the said units being provided with means housing exchangeable bridges, essentially constituted by at least one fusible unit or element, able to interrupt the connection between the cable connector and the pin or contact element when anything goes wrong in the electric current supply.

Although this structure is theoretically sound, it has never achieved general acceptance due to the fact that by way of conducting bridge a wire has been used having a virtually capillary diameter, for instance provided on a dielectric carrier member in the form of a plate, which Wire having a capillary diameter when fused tends to obstruct the investigation of the defect, which in itself is irritating, especially in the case when two or more bridges are provided in one plug, due to the fact that it is necessary to take out two or more bridges from the same in order to make sure that the damaged bridge has been located and a new one substituted in its place. Another-drawback of the known security plug consists in that, in order to change a burnt bridge the same has to be located at a place far away from the service posi- Patented May 28, 1957 tion of the said plug, the said fact increasing the drawbacks of the case.

The primary object of the present invention is to start from what is known about the subject and to introduce certain modifications which are intended to remove the drawbacks the known security plugs are suffering from.

For a better understanding of the object of the present invention a preferred embodiment of the same has been illustrated by way of example in the accompanying drawing, in which:

Figure l is a front elevation on one of the larger faces of the box of the improved plug, the lid shutting off the interior of the said box having been removed;

Figure 2 is an axial elevation looking onto the end of the box through which the cord enters the interior of the same;

Figure 3 is an entirely diagrammatic horizontal transversal section illustrating the active position of the conducting bridges and of the spare bridges which are housed within the said box made of dielectric material;

Figure 4 is a view similar to that of Figure 1, in which the box is shown with the lid on, the said lid being provided with security means preventing the same from unduly coming off;

Figure 5 is a fragmentary view of the flexible clamp holding the exchangeable bridge which clamp is fastened onto every one of the cable connectors of the security P Figure 6 is a fragmentary view of the flexible clamp holding the exchangeable bridge, which clamp is fastened onto every one of the pins of the security plug, both Figures 5 and 6 illustrating one of the many possible ways of using the said flexible clamp in combination with the remainder of the improved security plug;

Figure 7 is a front elevation of another preferred embodiment of the improved plug;

Figure 8 is a front elevation of the improved plug, in which the lid is somewhat shifted so as to show the removable block provided in order better to secure the lid, the said block constituting, furthermore, a sort of wedge separating the cores of the cord entering the hollow body of the plug under review;

Figure 9 is a fragmentary view similar to that of Figure 6 illustrating a modification in the structure of the body of the pin; and

Figure 10 is a view in perspective of the removable block.

With reference now to the accompanying drawings, the improved electric security ping 1 is essentially constituted by a box 2 with preferably two cable connectors 3 and 4 and two pins or contact elements 5 and 6. The

cable connectors 3 and 4 as well as the pins or contact elements 5 and 6 are constituted by separate elements placed at a distance from each other, the said elements being provided with means admitting an exchangeable bridge 7 essentially constituted by at least one fusible unit or element, preferably provided on or within a supporting means 8 provided at its end with contact means 9 for originating electrical conduction between the admitter means and the respective exchangeable bridge 7. As a rule, these admission means are suitably constituted by a clamp having flexible prongs suitably and conductively fixed to the respective portion of each cable connector 3 and 4 and of each pin or contact element 5 and 6.

The hollow interior 10 of the box is suitably divided into several compartments by means of partition walls 11, 11' and 11", one of the said compartments, referred to as 12, houses the cable connectors 3 and 4, whilst compartments 13 and 14 house the exchangeable bridges 7 and the remaining compartment 15 is so arranged as to receive the spare bridges 7, all of the said compartments opening onto one of the larger sides of the box constituted by a removable lid 16 provided with pertinent fastening means. i

The said removable lid 16 may be constituted by a plate-shaped element with at least two'bevelled edge zones acting as enchasing blades 17 slidable in the respective grooves 18, provided in pertinent portions of the box 2. This structure has the advantage that the box remains perfectly smooth on the outside so that it is easy and comfortable to hold.

The same lid may be constituted also by a suitable element provided axially and over its larger side with a fluted recess with longitudinal sides bent outwardly and towards the base of the recess, thus forming a setting into which may he axially inserted the complementary longitudinal' sides of a protruding square solidary with the dielectric body of the plug around the open portion of the respective larger side of the same.

The distribution of the compartments is planned in such a way that the compartment 12 housing the cable connectors 3 and 4 is horizontally placed at the inlet end of the electric cord 19, whilst the compartments 13 and 14 housing the conductor bridges are placed laterally and perpendicularly with respect to the horizontal compartment 12, compartment 15 housing the spare bridges 17' being inserted in between the two lateral perpendicular compartments 13 and 14.

The partition walls 11, 11 and 11" constituting a T-shaped geometrical pattern of two bars spaced from each other may be either a combination solidary with the rest of the box 2 or an individual combination which may be fitted into the said box, to which end the respective surrounding walls of the said hollow interior being provided with bevel grooves 20 fitting the ends of the said partition walls which it is desired to enchase.

The horizontal partition wall 11 constitutes at the same time a support for the cable connectors 3 and 4, each of the said cable connectors consisting of an L- shaped metal element 21, one arm of which is provided with an internally threaded perforation into which is inserted a screw 22 securing the bared end of the respective core of the electric cord 19, whilst the other arm of the L-shaped element is provided with a perforation in engagement with a conductor screw 23 which, penetrating through a passage 25 provided in the partition wall 11, is able to connect and secure the L-shaped element onto the pertinent flexible clamp 24. (See Figure 5.)

The wall 2 of the box 2 supporting the pins and 6 is provided with passages 25 into which are inserted the screws 27 securing and connecting the respective pin onto i the pertinent flexible clamp 28.

Every exchangeable bridge 7 is constituted by at least one capillary wire housed within a transparent tube 8 hermetically closed at its ends by means of caps 9 conductively engaging the said flexible clamps with the capillary wire, the hermetically closed interior of each transparent tube 8 containing a substance or chemical compound able optically to signal by coloring, opacity and such like the fusion of the said wire.

As may be appreciated in Figures 1, 2 and 4, on the one hand, and Figures 7 and 8, on the other hand, the lid 16 may be removed from the body 2 by sliding it either in the direction of the electric cord 19 or in the direction of the length of the pins 5 and 6.

This latter embodiment has the advantage of preventing the removal of the lid 16 when the plug 1 is in the outlet. Thus a high degree of security is obtained against incidents or accidents which may be fatal.

Yet another advantage of the latter embodiment consists in that the said lid 16 may be secured to the body 2 in an even better way by inserting the block 34) constituted by a body of any suitable shape which may be introduced into the upper transversal compartment 12 of the interior 11) of the box 2, the said block 30 being provided with an internally threaded cavity or perforation 31 housing the fastening means 29 of the lid 16 and, on its upper portion, with a groove 32 sloping at both sides and serving as a guide for the cores of the cord 19 directing them towards the cable connectors 3 and 4. In this manner another advantage is gained which consists in that the said block 36 serves at the same time as cores separator and as a security barrier between the two cable connectors 3 and 4 excluding the danger of a conductor bridge being formed between the same which would 'cause a short circuit.

In order that the said block 30 may be correctly placed in the compartment 12 of the interior 10 of the box 2, the said block 30 is provided on at least one of its larger upper and lower sides with a projection 33 in operative engagement with a registering recess 34 suitably provided in the box 2 or, respectively, in the partition wall 11. Apart from the exact fabrication of the block 30, the combination of this projection 33 and the recess 34 guarantees also the perfect stability of the same which conveys to the hollow box 2 a greater mechanical breaking strength.

In order to eliminate the possibility of touching the pins 5 and 6 whilst still partly plugged in the outlet, the usually cylindrical body of each pin may be provided with a portion of reduced diameter 35 having the shape of a preferably cylindrical pin inserted into a removable insulating sleeve 36.

Before connecting the improved security plug 1 with the electric cord 19 of an electric gadget, the bridges 7 and 7' are chosen in accordance with the maximum amperage of the said electric gadget, the active bridges 7 being so placed in compartments 13 and 14 as to enable their caps to be gripped by the flexible prongs of the respective clamps, whilst the spare bridges 7' are housed in compartment 15. Once the said bridges are correctly placed, and the bared terminals of the cores of the electric cord are connected onto the cable connectors 3 and 4, the lid 16 is slid into place along its setting until the entire month of the box 2 is covered, after which it is secured by one or more fastening means 29.

Should an interruption of the supply of current happen due to the fusing of one of the two active bridges 7 of the security plug, it is sufiicient to loosen the fastening means 29, remove the lid 16 by sliding it as above explained,

' examine the bridges and substitute a spare bridge taken from compartment 15 for the fused one which is easily located due to the coloring, opacity or any other predetermined signal given by the substance contained in the transparent tubes 8. It is advisable to replace the spare bridge before closing the lid 16 so that the plug and electric gadget be in perfect condition before being used again.

As to the said block 30, it should be pointed out that the same serves not only for securing the lid 16 but also for guiding the cores of the electric cord, in which case the groove 32 sloping at both ends shall have a suitable depth fitting the outer diameter of the insulating lining of each core which it is desired to secure.

It is understood that suitable modifications may be made in the structure of which several embodiments are here disclosed, provided such modifications come within the spirit and scope of the appended claims.

What I claim is:

1. An electric plug comprising a box of a non-conducting material with a removable cover, and three partition walls in the box with two of the walls being spaced parallel to each other and the third wall being at right angles to the two parallel Walls at one end thereof to form a T-shaped wall structure with two parallel spaced leg parts, said box being internally divided by said partition walls into a compartment housing cable connectors, two individual compartments for fuse bridging means, connecting each cable connector with a contact pin, and a compartment for housing spare bridging means.

2. An electric plug in accordance with claim 1, in which each pin is supported by a screw penetrating into an end of the said pin and passing through an opening formed in a lateral wall of the said box, said screw locking a clamp for supporting the corresponding end of the bridging means at the other side of the said wall.

3. An electric plug according to claim 1, in which each bridging means is formed by a fuse extending into a tube of transparent material closed at both ends by cups of conducting material, the interior of the said tube containing a substance capable of optically signalling the blowing of the fuse.

4. An electric plug according to claim 1, in which each pin has an inner end portion of reduced diameter, the said portion being protected by a changeable insulating sleeve.

5. An electric plug comprising a substantially elongated fiat box of quadrangular section with a slidable lid for closing the opening provided at one of the two larger sides of the said box and fitted to the longer lateral walls of the said box by a tongue and groove joint, and three partition walls in the box with two of the walls being spaced parallel to each other and the third wall being at right angles to the two parallel walls at one end thereof to form a T-shaped wall structure with two parallel spaced leg parts, said box being internally divided into a transversal compartment for cable connectors, situated at one end of the plug, and limited by the transversal partition wall and longitudinal compartments, separated by longitudinal partition walls, extending substantially at right angles to the transversal compartment, for housing fuse bridging means connecting the cable connectors with contact pins protruding at the opposite end of the box, and for housing spare bridging means.

6. An electric plug according to claim 5, in which the partition walls are constituted by a single unit fitted into the said box, the lateral walls of the said box being provided with grooves for housing the lateral edges of the said partition walls.

7. An electric plug in accordance with claim 5, in which the transversal Wall partition is provided with openings for screws fixing L-shaped cable connectors to one side of the said wall and clamps for holding an end of the corresponding bridging means to the other side of the said wall.

8. An electric plug comprising a box of a non-conducting material with a slidable lid and dividing walls, the said box being internally divided into a compartment by the walls for housing the cable connectors and individual compartments for fuse bridging means and spare fuse bridging means, a forked block with guide surfaces insertable in said first mentioned compartment, said forked block comprising a projection fitting into a registering groove provided on a lateral wall of said compartment, and a holding screw for locking said cover to said forked block.

References Cited in the file of this patent UNITED STATES PATENTS 1,892,567 Craddock Dec. 27, 1932 2,225,718 Sheppley et al Dec. 24, 1940 2,528,971 Philips Nov. 7, 1950 2,668,885 Gerlat Feb. 9, 1954 

